1. Field of the Invention
The present invention relates to a manufacturing method of a friction plate used in a lock-up clutch device or the like which is used in the automatic transmission of a vehicle and a manufacturing apparatus of the friction plate.
2. Related Background Art
Recently, the use of a friction plate obtained by adhering frictional material segments to a core plate has been proposed for the purpose of enhancement in throughput of the frictional material from requirements of the cost reduction. With the proposal of the use of the friction plate, a manufacturing method of the frictional material for adhering the frictional material segments and the manufacturing apparatus thereof have been developed.
In such conventional manufacturing method (and the manufacturing apparatus), a manufacturing method of the friction plate comprising steps of advancing a frictional material at a desired interval to punch so that frictional material segments are obtained and directly press-adhering the frictional material segments to a registered core plate has been known. In this method the punching of the frictional material and the press-adhesion are performed in a series of operations by using the same member and the core plate is indexed (rotated) at a desired angle in accordance with these operations.
FIG. 11 shows a conventional manufacturing apparatus of the friction plate. The manufacturing apparatus thereof will be described below. As shown in FIG. 11, a frictional material 131 advanced at the same pitch with a punching device 100 is punched to obtain a plurality of frictional material segments 132. On the other hand, a circular table 110 has a supporting rest 111 and registers a core plate 121. The frictional material segment 132 obtained with the punching device 100 is punched with a punch 101 in accordance with the shape of a mold 102 and is press-adhered to the core plate 121. The supporting rest 111 is indexed at a desired angle in a range to which the frictional material segments 132 were adhered so as to conform to the operations of the punching and press-adhesion operations. Such kind of conventional techniques include those disclosed in for example Japanese Patent Publication Nos. 4-68491, 4-68492 and 4-68494, and Japanese Laid-Open Patent Application Nos. 7-151175 and 10-318309 and the like.
However, to manufacture a number of friction plates with a higher production efficiency in a short amount of time using these conventional techniques, it is necessary to perform operations of punching, press-adhesion and indexing at a higher speed. Therefore, there are problems such that the pressing time becomes short in the press-adhesion in these series of operations and it is impossible to obtain sufficient adhesion forces. Further, after the press-adhesion of the frictional material segments, the frictional material segments are immediately indexed, whereby position shift of the frictional material segments can easily occur. Thus, it is difficult with conventional methods and devices to increase the speed of manufacturing a friction plate because of the position shift problems associated with speeding up the indexing operations.